Your search for "Shelley Minteer" returned 51 results

Acetone is one of the most abundant volatile organic compounds (VOC) in human breath and high acetone levels result in ketoacidosis. Many acetone sensors have been developed; however, many disadvantages are present; therefore, there is a need for a more specific, biologically friendly, and simpler biosensor for breath acetone detection for diabetics. This study outlines a procedure for isolation, purification, and characterization of NADPH-dependant carbonyl reductase enzyme for use in an amperometric acetone sensor. Carbonyl reductase was extracted from Saccharomyces pastorianus yeast cells and purified using column chromatography. Carbonyl reductase activity was evaluated using activity assays and was also studied electrochemically. Furthermore, this study outlines a procedure for a flow injection method used for detecting aqueous acetone in the presence of carbonyl reductase. Lastly, various immobilization techniques were tested in order to improve current response and the selectivity towards acetone.

The field of biological fuel cells has been exponentially expanding over the last decade. As the fundamental science has evolved and improved electrode performance, more focus has been paid to engineering design of the biological fuel cell. This review details the transition from U-cell designs to MEAs to other form factor-based biological fuel cell designs, depending on the energy applications.

A biological fuel cell is a device that converts biochemical energy into electrical energy using a biocatalyst. The basic principle is that the process of fuel (substrate) oxidation by microorganisms or enzymes in the fuel cells offers electrons and protons for electricity production. This paper details the development of bilirubin oxidase biocathodes for ethanol/oxygen biofuel cells. In the described configuration, both the anode and the cathode electrodes in the biofuel cell employ biological catalysts (enzymes) instead of traditional metallic fuel cell catalysts. This enzymatic biofuel cell employs alcohol dehydrogenase to oxidize ethanol at the anode and bilirubin oxidase to reduce oxygen at the cathode. This ethanol/oxygen biofuel cell has an active lifetime of about 20 days and shows power densities of up to 1.67mW/cm2. The biocathode described in this paper is unique in that bilirubin oxidase is immobilized within a modified Nafion DE520 polymer that acts both to entrap and stabilize the enzyme. The biocathode is fuel tolerant at low fuel concentrations (1mM), which leads to a fuel cell that employs both renewable catalysts and fuel, but does not require a separator membrane to separate anolyte from catholyte.

Incorporation of multiple enzymes on electrode surfaces can enhance the fuel efficiency of biofuel cell anodes, by sequentially catalyzing intermediate reactions such that fuel is completely oxidized. A quantitative study of multiple enzyme systems immobilized on porous electrodes is presented, considering immobilization of all enzymes uniformly codispersed in the same phase, as well as dispersion of individual enzymes in separate phases. Multiple phases maintain nonuniform pH conditions to enable optimum activity of each enzyme, while offering exposure to a common to the anode surface where the cofactor acting as a mediator may undergo oxidation. Comparisons have been made with the performance of electrodes with all the enzymes in a single electrode phase, identifying kinetic and transport conditions under which multi-phase immobilization shows improvement over single phase systems. The models are applicable to more electron rich enzyme reaction systems.

Although pyruvate has not been considered as a fuel for an enzymatic biofuel cell, there are dehydrogenase enzyme capable of oxidizing pyruvate. This paper details the discovery of a pyrroloquinoline quinone-dependent pyruvate dehydrogenase (PQQ-PDH) in Gluconobacter species. A method was developed to isolate and purify PQQ-PDH from Gluconobacter, along with the characterization of the purified enzyme. It was found that the purified enzyme can undergo direct electron transfer at carbon electrodes surfaces, which allowed for its incorporation into a pyruvate biofuel cell. It was also found that PQQ-PDH lacks substrate specificity, which minimizes its usefulness in many sensor applications, but is advantageous for deep oxidation in biofuel cell anodes.

Chitosan, a biopolymer extracted from crab shells, was combined with silica spheres and cobalt chloride in concentrations ranging from 0 to 10 mM and cast onto Toray paper electrodes over a 1 cm2 area. The electrodes were then pyrollyzed via ohmic heating by passing current through the electrode for 5 minutes under an argon environment. The silica spheres were then removed to leave a porous scaffold, by soaking the electrodes in 30% KOH. Analysis of these mesoporous structures as possible cathode materials was done by microscopy and voltammetry.

Thylakoid membranes have been proposed for electrochemical solar energy conversion, but they have been plagued with short term instability. In this paper, thylakoid membranes extracted from Spinacia oleracea were physically adsorbed onto Toray paper electrodes with and without catalase, followed by entrapment in a vapor deposited silica matrix. The bioelectrodes were tested using voltammetry and amperometry and tested in a complete photobioelectrochemical cell. Upon subsequent polarization experiments, a significant decrease in the maximum current density from 1.53 ± 0.13 μAcm⁻² to 0.75 ± 0.14 μAcm⁻² was observed without catalase present. When catalase was included in the anode, this current decrease was not observed, showing the importance of catalase to scavenge reactive oxygen species produced by the thylakoids during photoelectrocatalysis.

Carbon quantum dots (CQDs) were incorporated into thylakoid bioanodes capable of direct photobioelectrocatalysis in order to increase the photocurrent generation. More thylakoids are in contact with the increased surface area which allows for greater direct electron transfer (DET). Additionally, the fluorescent quantum dots redshift the light which allows for the thylakoid/CQD electrodes to use more of the solar spectrum, increasing the photocurrent. The current density was more than twice as large when CQDs were included in a thylakoid bio-solar cell.

The performance of biofuel cells with enzyme cascades have normally been characterized with open circuit potential, power density, and current density measurements. In this work, we demonstrate that with the method of quantitative product analysis by mass spectrometry, we can obtain other valuable information about the biofuel cell efficiency. Faradaic efficiency, coulombic efficiency and product efficiency were calculated for a six-enzyme glucose biofuel cell system. Oxidation pathway bottlenecks were determined with quantitative mass spectrometry measurements via direct infusion. These measurements and calculations give an in-depth understanding of the bioelectrocatalytic bottlenecks in the enzyme cascade for the target fuel (glucose).